Blog of the Rouge River Bird Observatory
at the University of Michigan-Dearborn

Friday, September 5, 2008

Week #3 in review

Although spring warblers are bright and colorful, I have always enjoyed fall banding the most. The pace is steadier and a little less weather-dependent, and I like seeing all the young birds and gauging the success of the breeding season. The nice variety of bird species which inevitably begins in September makes up for the inescapable reality that winter is on the way.

The Nashville Warbler (Vermivora ruficapilla) above was, as are over 80% of the fall birds we band, a hatching-year (HY) bird. Nashville's have a very protracted fall migration, with the earliest records from late August, and some lingering into early November.

Blackpoll Warblers (Dendroica striata) are one of my favorite species. In the field, they can be hard to distinguish from Bay-breasted and Pine Warblers in the fall, and these three species are the classic "confusing fall warbler" complex. In the photo above, you can't see the yellow feet, which help distinguish this species. McGill Bird Observatory has a nice guide to the fall warblers.

Magnolia Warbler (Dendroica magnolia) is one of our top-ten most frequently banded species. In all seasons, they show a pretty wide variation in plumage, from dull young females to bright old males. Because of this variation, banders are not "allowed" to sex HY Magnolia Warblers (if we submit records to the federal Bird Banding Lab that say a HY Magonlia is a male or female, we are told to change the sex to "unknown"). However, very dull birds with short wings are likely female, so for this bird, I noted "female" -- but only in the comments of our data form.

At the other end of the spectrum are most small Empidonax flycatchers, in which not only do the ages and sexes look alike, but so do many species. Wing and bill measurements, and examination of the shape of some of the feathers helps tell apart many of the species in the hand. For the most part, however, Willow and Alder Flycatchers (E. trailli and alnorum) cannot be told apart in the hand. We submit them as "Traill's" Flycatchers.